1. Field of the Invention
The present invention relates to a control device for a safety free-wheel coupling, adapted to be mounted on a motor vehicle transmission shaft.
Numerous free-wheel coupling devices have already been proposed, either for machine-tools or for motor vehicles.
Thus, French Pat. No. 1 157 423 (RENAULT) describes a free-wheel coupling system which cannot be engaged at all speeds, and whose engagement is solely manual and not automatic. This device, provided normally for a machine-tool, is too cumbersome to be mounted on an unequipped transmission shaft and cannot therefore be adapted to the transmission shaft of a motor vehicle. This remains why it is in fact unused.
U.S. Pat. No. 3,188,435 relates to a free-wheel system, which is only engaged from a certain speed and which is therefore dangerous. Moreover, no safety means are provided in this device.
U.S. Pat. No. 2,012,087 relates to a device for coupling two shafts together for machine-tools, allowing uncoupling in only one direction. This extremely cumbersome device cannot be adapted to a motor vehicle shaft.
U.S. Pat. No. 2,283,965 relates to a system for coupling two shafts together which can only provide this coupling in a single direction of rotation.
Now, in a free-wheel coupling for motor vehicles, it is indispensable to have the ability to couple in both directions of rotation.
The object of the invention is to provide a free-wheel coupling control device for motor vehicles which is relatively simple in construction, compact and consequently easy to mount on an unequipped transmission shaft, and very reliable in operation. In particular, the aim of the invention is to provide a conrol device which allows the wheel of the vehicle to be recoupled automatically to the associated transmission shaft from a certain forward speed, and this for obvious safety reasons. The invention also aims to allow the automatic re-establishment of the engine brake at the same time as the recoupling of the two shafts during braking, without any action being required of the user.
The advantage of the free-wheel couplings provided by the invention consists essentially in the substantial saving in fuel offered by low speed devices, mainly in urban areas, because of the recovery of the inertia of the vehicle.
However, because the friction between the wheels of the vehicle and the ground is considerably reduced when the wheels are uncoupled from thair drive shaft, it will be readily understood that the safety of the driver requires instantaneous recoupling of the wheel and the transmission shaft in certain predetermined speed ranges and in the case of braking, while ensuring recovery of the energy lost during engine brake.
The control device provided by the invention is adapted to be mounted on a motor vehicle transmission shaft between a first driving part of this shaft and a second driven part of said shaft driving a wheel, and it comprises means for coupling the driving shaft and the driven shaft together in both directions of rotation thereof and for uncoupling the driving shaft from the driven shaft in the direction of rotation corresponding to forward travel.